Tensioning devices comprising a chain tensioner and a tensioning rail are used quite generally where chain drives are used. A preferred field of application is the use in internal combustion engines in which a timing chain drive drives the camshaft by means of a timing chain. In this field of use, high demands have to be satisfied with respect to the strength of the tensioning rail and the sliding and guiding characteristics in the area of contact with the circulating endless drive means, since the endless drive means, which is normally a drive chain, must be kept under a defined tension during operation. In addition, the tensioning device compensates manufacturing tolerances and an elongation of the endless drive means occurring during prolonged use. Conventional tensioning rails consist either completely of a suitable plastic material having a sliding surface for contact with the endless drive means or of a support body provided with a sliding lining. The support body, which may be configured as a metal carrier or as a fiber-reinforced plastic profile, may be provided with a separate low-friction sliding body so as to form the sliding lining in the area of the surface contacting the chain.
DE 24 31 425 A1, by way of example, discloses a tensioning rail whose support has applied thereto a heat-resistant polyamide plastic as a sliding lining. Another tensioning rail comprising a support body made of fiber-reinforced plastics and a low-friction sliding body is disclosed in DE 296 02 917 U1, the support body and the sliding body being produced separately of one another. In the case of a tensioning rail according to DE 43 103 06 A1, however, the sliding body is injection molded onto a support body of fiber-reinforced plastics by means of an injection molding process. Furthermore, reference DE 10 2004 058 948 A1 discloses a tensioning or guide rail in the case of which the sliding surface is wetted with a lubricant via a lubricant passage provided in the tensioning rail. In addition to non-uniform wetting of the sliding surface with the lubricant, a uniform supply of lubricant via respective feed passages is often problematic, especially in the case of tensioning rails.
Although many of the prior art structural designs of tensioning devices comprising tensioning rails for pretensioning endless drive means proved to be very useful, there are often problems and cases of use necessitating an adaptation of the structural design or a change of structure. Moreover, due to the general pressure for innovations in the field of automotive industry, it, is constantly endeavored to improve the components used and to adapt them to increasing demands.
It is therefore the object of the present invention to provide a tensioning rail having an optimized lubricant supply.